This invention relates to the quantitative determination of chemical oxidizing and reducing agents in a fluid environment. More particularly, the invention relates to the determination of chemical oxidizing and reducing agents by means of a novel type of sensor or detector which includes an ion-exchange membrane.
In the current state of the art, the electrodes forming a part of the electrochemical cell or couple in analyzers are separated from each other by means of a porous layer. The porous layer permits a restricted flow of electrolyte, thereby completing the electrochemical couple between the electrodes in the sensor portion of the analyzers. A serious disadvantage of the porous layer is that it permits a substantial diffusion of sample throughout the electrolyte between the electrodes. As a result, the recovery time necessary to stabilize known analyzers between tests is relatively long, and the only known way to reduce the recovery time is to provide special means of renewing the electrolyte in the analyzers. These special means are not entirely satisfactory in that they are cumbersome, costly, and require frequent and extensive maintenance. The present invention provides an analyzer which is not subject to the limitations of lengthy recovery time or the necessity of providing auxiliary means for re-stabilizing the electrode system.
A second serious disadvantage of the porous layer is that it is non-selective. The porous layer permits the electrodes to be exposed to all constituents of the fluid being monitored. The result is the possibility of contamination or poisoning of the electrodes, and of direct interference in the quantitative measurement by substances present in the sample other than those being determined. The present invention provides a means which, in combination with the electrodes, substantially eliminates the possibility of contamination or poisoning of the electrodes and of interference by extraneous components of the environment being tested.